Wireless mechanisms to actuate a motor, solenoid, or other device have been employed in a variety of products, such as garage door openers or vehicle locking mechanisms (e.g., unlocking a car door, opening a trunk, starting the engine, etc.). A pairing between a signaler (e.g., a wireless key-fob) and the actuator (e.g., a vehicle unlocking mechanism) can be used to add security to the process. Such pairing typically does not employ sophisticated encryption to reduce component costs and increase battery life in the signaler, for example.
Rolling codes (e.g., hopping codes) can be used to prevent replay attacks possible with simple pairing. A replay attack involves recording a previous transmission—such as using a radio receiver in proximity to the signaler being successfully used—and replaying the transmission in the future to achieve an unauthorized actuation. Rolling codes help to prevent this attack by defining a sequence of codes, a next code in the sequence used for a next actuation attempt. The signaler and the actuator store the sequence and maintain an index into the sequence that is incremented with each use. Thus, recording a previously used code in the sequence will not be accepted by an actuator because the actuator has moved on to another code in the sequence after the recorded code was successfully used.